#241  
Old 01-21-2018, 04:52 PM
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So HOW HOT does that Pontiac Blow thru Carb get? Show you a bit more math today.

Example: the inlet temperature is 70 deg F, the suction pressure is -0.5 psig (a slight vacuum due to Inlet Plumbing), the discharge pressure is 19 psig, and the efficiency is 72%. What is the discharge temperature?

Tin= 70 deg F + 460 = 530 deg R
Pin= -0.5 psig + 14.7 = 14.2 psia
Pout= 19 psig + 14.7 = 33.7 psia
Pout/Pin = 33.7/14.2 = 2.373 (this is the pressure ratio)
Tout = (530 + 530 x (-1+(2.3730) raised to the power of .263 ))) all of this divided by 0.72
= 717.8 deg R - 460 = 257.8 deg F
So the theoretical outlet temperature is 257.8 deg F. I sure would like to have an intercooler to cool that hot air down before it goes into my engine.

So assuming a 70% efficient inter-cooler

257 deg F – 70 deg F ambient temp = 187.886 deg F Temp rise from the turbocharger compressor

So if you have a 70% efficient inter-cooler: 188 deg f times .70 = 131 degrees of temp removal

So the discharger air out of the intercooler is 56 deg f hotter than ambient temp to the actual air
Temp going into the engine is 126 degrees at 19 psi boost pressure

This time I think the math will be easy to follow.

Tom V.

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  #242  
Old 01-22-2018, 09:48 AM
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Today I am going to talk about Holley carb floats.

First I will post up the normal "Stuck" Float, "Hung" Float, "Gas spewing out of carb" posts you find on the internet.

Then I will talk a bit about Holley Carb Float WEAR which all of the carb suggestions seem to ignore. If a Supply houise wants to sell you a new float why would they tell you have to fix a worn float so that you do not need to buy a new float?

So here is the normal stuff first:

The float on a Holley carburetor manages the amount of fuel present in the body of the carburetor at any point, allowing the metering blocks and power valve to serve atomized fuel to the intake plenum. When the float sticks, the regulation of fuel is disabled, incapacitating the car with a flooding or lean condition, the latter being potentially damaging to the engine if operated for an extended period of time. A stuck float may be caused by fuel residue within the float valve, a poor valve seat or debris lodged in the fuel bowl area.

Remove the fuel bowl bolts with a 5/16-inch wrench and pull the bowl off the metering block.

Examine the movement of the float with your finger. If the fuel bowl is stuck in position, REMOVE ANY DEBRIS that may be present and spray the bowl with carburetor cleaner spray. Test the movement again to see if this fixes the problem.

Remove the adjustment screw and nut from the exterior of the bowl with a screwdriver and open-end wrench. Pull the valve from the valve seat and INSPECT IT FOR FLAWS. Spray it clean with carb cleaner spray and REPLACE IT if the tip of the valve (where the valve seats) is damaged or worn. Insert the valve in the seat and reinstall the adjustment screw and nut. (A float level adjustment will be needed once the bowl is reattached to the carburetor).

Nothing about the wear point on the float where the float CONTACTS the Needle and seat
See link to Video attached. You do not need to actually open the video, I just want you to see the contact point on the float arm where the needle contacts the float.

All Holley Floats have a "Hill" (Raised Area) on the float arm that contacts the needle.
THIS HILL ACTUALLY DOES WEAR OVER TIME BECAUSE THE HILL IS BRASS or soft steel attached to the brass float AND THE NEEDLE IS HARD STEEL. So when you have wear you can have a ledge/divit formed on the "Hill" being the weaker material.

The Divit now gives the needle a place to hang up vs move smoothly thru its arc.

When this occurs you can trap foreign material in the divit or you can get a rough spot on the float arm where the arm sticks.

So the fix is to inspect the "Hill" on each float and make sure that it is smooth and the float travels easily over the "Hill" and controls the fuel coming into the bowl properly.

That being said the Supply houses still want to sell you a new float because it is "filled with fuel", etc when it reality the float just needs a bit of polishing.

Floats are not cheap from the supply houses.
$12.00 or more for 1 float that may just need a bit of polish on the "Hill"

Here is the link to the video but just look at the video screen, no need to open the video.

http://www.jegs.com/p/Holley/Holley-...43657/10002/-1

Tom V.
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Last edited by Tom Vaught; 01-22-2018 at 09:56 AM.
  #243  
Old 01-22-2018, 10:32 AM
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Didn't see a video Tom, just a Jegs float and hardware page.

Edit: BTW, appreciate the elaboration, your math skills are pretty wicked to say the least and as such a bit difficult to follow.

That last equation however does a great job of illustrating the formula for us math deficient fellas .

As Always Much Thanks,

Frank

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Last edited by 4zpeed; 01-22-2018 at 10:59 AM.
  #244  
Old 01-22-2018, 03:20 PM
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The video should be farther down the page and show the raised "hill" that the needle rides on 4zpeed.

Tom V.

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  #245  
Old 01-22-2018, 03:56 PM
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http://www.jegs.com/p/Holley/Holley-...43657/10002/-1

Copied and pasted the link, I'm aware of the "Hill" you're referring to, just wondering for the sake of others.

Could be I'm just not getting the pop up, perhaps I didn't hand crank ye ol laptop appropriately this morning!

That or I'm video deficient as well...


Thanks

Frank

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Last edited by 4zpeed; 01-22-2018 at 04:04 PM.
  #246  
Old 01-22-2018, 04:21 PM
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You and others will be fine now.
When you have the person next to you and you can point and say, that COULD be the reason why the float is not working correctly is a lot different from making a post and trying to the figure out how to explain it is just words.

All that being said, I am glad that I could pass on that tip that might resolve a float hanging issue on the carb, without spending $$$.

Tom V.

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  #247  
Old 01-24-2018, 09:10 AM
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Today going to post a bit about Holley WET FLOW TESTING, Holley's Wet Flow Bench, and A bit more on why the Main Jets could be removed on the Main Circuit and still not affect the Idle Fuel Mixture much, in some cases. Opening the Power Valve (blocked signal that would normally keep it closed might have more of an Idle effect).

What does "100% wet tested" mean?

Wet tested means the carburetor is tested with air and fuel flowing to simulate actual engine operation. The test stand is comprised of a large vacuum pump and fuel supply. A fuel line is connected to the carburetor using mineral spirits at 6 psi (typical). The test stand is instrumented to measure fuel flow and air flow. The vacuum pump is turned on, and air and fuel will flow through the carburetor in the same way as on the engine. From this the A/F ratio can be calculated. The idle airflow and fuel flow is adjusted to spec, then the A/F ratios at different throttle positions representing off-idle part throttle and full throttle are measured. If the flows do not meet specification, the carburetor will be inspected and parts replaced as necessary to make sure it is correct.

Holley has a Wet Test Stand that has a 6000 cfm flow capability. (originally used for WW-II LARGE Aircraft Engine Carburetor Testing).

The Stand has special Radiused Inlet Orifices, only one used at a time, that controls the 100% air flow capability for that Flow Test.
The air goes thru the "Orifice", then thru large piping to a Special "Test Box" that can be sealed up so there is no air leakage. It can also be raised up to allow mounting a carb inside the bench on the flow fixture, hooking up the fuel line to the carb, and the throttle linkage.
The "wet stand" uses Stoddard Solvent, a much safer flow liquid vs gasoline to simulate the gasoline in a normal engine. It has a similar Specific Gravity. So air goes Thru the orifice, into the pressure box, into the carb, out of the carb, and after fuel is removed back to the atmosphere. The throttle changes the air flow read by the calibrated flow orifice.
(From the carburetor Flow Box the air/fuel mixture goes to a fuel separator where the Stoddard Solvent is reclaimed for use in another test. The air is cleaned and passed back into the atmosphere). So no air pollution.

The carb is flowed at multiple test points. Graphs are created for each carb circuit and test points recorded with the measured data.

Topic #2

The Idle Circuit and the Main Circuit.

Because the IFR (Idle Feed Restriction) is connected to the Main Well, fuel flow through the IFR will be affected by the fuel level in the Main Well. Think of it as the Idle and Main systems playing tug of war.

At idle, the Idle system draws fuel from the Main Well. Since the Main Jet offers some restriction, the fuel level in the Main Well drops.

This results in a lower head of fuel (height of the fuel above the IFR). If the Power Valve is open, it’s just like opening up the Main Jet. This lower restriction raises Main Well fuel level and the Idle air/fuel ratio becomes richer.

It is by design that the Idle Circuit feeds from the Main Well. With the Idle System pulling the Main Well level down, a higher airflow is required to get the Main System started. This helps prevent the Main Nozzle (boost venturi) from dripping or starting prematurely. (If you have the fuel level too high in the Fuel Bowl you can get Nozzle Drip too). As the throttle is opened, the Venturi Signal increases, and the Idle Signal eventually DECREASES, (but does not stop) so there is a smooth transition to the Main System. When the throttle is opened suddenly, the Idle System drops out (stops) because it is sensitive to Vacuum, not Airflow. This raises the fuel level in the Main Well and the Main System will now start faster to compensate for the WEAKER Idle Signal.

You can observe this effect - with the vehicle in neutral, open the throttle with the idle speed screw slowly until you see fuel flow just beginning to discharge from the Booster. Holding the Throttle at this position, open the Mixture Screw and the Nozzle should stop.

This is common Carburetor Theory that is taught to every Carb Engineer at Holley so you could hear the same exact explanation from different Engineers but the Holley Carb principals will not change.

Tom V.

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Last edited by Tom Vaught; 01-24-2018 at 09:18 AM.
  #248  
Old 01-25-2018, 10:52 PM
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Tonight, I am going to talk a bit more about the Holley carb drillings and circuits of the typical 4150 Double Pumper Carb, specifically the Main Body with a "close up" picture. If you click on the image it will be much easier to see the different passages and their hole markings.

1) Because the Choke Mechanism is located on the left side of the picture there are two clues to which end of the Holley Carb we are looking at Primary? or Secondary?

There is also the Carb "List Number" 4779-9 showing on the Choke Tower so we know that the Carb is revision #9 of the Holley 4779 (750 cfm)
Double Pumper Carbs.

2) The Holes in the Main Body "face" are labeled "A", "B", "D", "E", "F", "G", "H", and "I" on the picture.

"A" is the drilling that goes to the Idle Air Bleed inside the air horn of the carb
"B" is the Accelerator Pump drilling that supplies fuel to the "Accelerator Pump Squirter"
"C" is not shown on the picture but should be a vertical drilling below the Letter "F" that supplies a
Vacuum Signal to the Power Valve Chamber "F"
"D" is the drilling that goes to the High Speed Air Bleed inside the air horn of the carb
"E" is the Main Well Passage that supplies fuel and air mixture (from the Emulsion Jets and the Main Jet)
to the Carb Booster) inside the air horn of the carb
I have mentioned "F" previously
"G" is the drilling for the Ported Vacuum Signal to the Distributor
"H" is the Air and Fuel feed passage to the Idle Mixture Screw
"I" is the discharge passage from the idle mixture screw which then goes downward to the Throttle Base Plate

There are two "Dimples in the Main Body gasket surface. Those holes have cast pins that fit into them and
hold the Holley gaskets in the right location on the Main Body surface.

On the outside perimeter are 4 threaded holes that the Bowl Screws thread into that hold the Fuel Bowl,
the Fuel Bowl Gasket, the Metering Block, the Metering Block Gasket securely against the machined Carb
Main Body surface.

So that is a short description of the Drillings on the Carb Main Body.
Have a nice evening.

Tom V.
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Last edited by Tom Vaught; 01-25-2018 at 11:21 PM.
  #249  
Old 01-28-2018, 10:33 AM
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Maybe do some additional info on the TRI_POWER stuff as there was a guy looking for air cleaners for EFI Throttle Bodies that looked like Holley 6 Pack/ Corvette Carbs.

Back on Monday.

Tom V.

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  #250  
Old 01-28-2018, 05:46 PM
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The topic today is Tri-Power Air Cleaners, Holley Air Cleaners and even a link for Rochester Tri-Power Air Cleaners.

O'Brian Truckers is located in Charlton, Massachusetts and makes a really nice set of Air Cleaners for the Holley and Rochester Tri-Power Carburetor systems.

Several Links, just click on them and see what is available. I do not believe that this info in any way would affect Ames Performance sales.

https://www.obrientruckers.com/ecom/category/239/

https://www.obrientruckers.com/ecom/category/239/
Bases: Round air horn sizes of 2 5/16" for 1 BBL's, 2 5/8" set screw or center hole bases for 2 BBL's and 3 1/8" set screw or center hole bases for 2 BBL's.

Three polished finned covers and special "D" shaped cast aluminum bases.

https://www.obrientruckers.com/ecom/category/239/

The Mopar/ GM Air Cleaners are 'rounded corner' "D" shaped on the Air Cleaner Retention Ring.
The Ford Air Cleaners are 'sharp corner' "D" shaped on the Air Cleaner Retention Ring.

I own 3 sets of the air cleaners. 2 sets for the Holley Systems I have and one set of air cleaners for the modded 4412 500 cfm 2 bbl carbs I built up.

Tom V.

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  #251  
Old 01-28-2018, 05:49 PM
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Links in previous post
Pictures below

Barry Grant/GM/MOPAR 1st pic

Rochester Tri-Power Carbs 2nd Pic

Tall 2.5" K&N Filter for air cleaners 3rd Pic

Tom V.
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  #252  
Old 01-29-2018, 07:31 AM
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In Post #248 I showed you a Main Body picture and typed up the different circuits in relation to the Letters on the picture.

Today I will do the same for the metering Block except that I found an article from a Magazine on the web that saves me some typing.

(B) Idle downleg:
This passageway feeds fuel to both the idle discharge port and the idle transfer slot.
(C) Idle well:
Fuel from this well travels to the top of the metering block, then turns 180 degrees and mixes with air from the idle air-bleed into the circuit.
(D) Accelerator pump passage:
This transfers fuel from the accelerator pump to the outlet nozzle.
(E) High-speed air-bleed:
Air from the high-speed bleed enters the metering block here to be mixed with the fuel as it climbs the emulsion tube.
(F) Passage to booster:
This channel transfers fuel from the main well to the booster
(G) Ported vacuum passage:
This connects the ported vacuum source in the throttle body to the outlet where this can be routed to a source like vacuum advance.
(H) Parallel air well:
Air is introduced into the main well through these two holes.
(I) Main well:
Fuel collects here after passing through the main jet.
(J) Power valve channel:
This is where the power valve is located. The two small holes are the power valve channel restrictors (PVCR) that determine the amount of fuel added to the main metering circuit when the power valve opens. This valve determines when additional fuel is added to the main circuit.
(K) Idle restrictor channel:
Fuel from the main circuit passes through this short channel and through a small brass restrictor (L) that acts as the idle circuit jet.
(M) Idle transfer slot discharge:
Idle fuel exits the metering block to deliver fuel to the transfer slot.
(N) Idle fuel discharge port:
Idle fuel exits the metering block and enters the carburetor main body for carb idle fuel below the throttle blades.
(O) Dowel pin:
Two pins locate the metering block on the carburetor main body.

The info in the article is pretty good so I posted it as published.

Bowl Side of Metering Block

Bowl Side of Metering Block
(A) Timed spark port:
This outlet supplies ported manifold vacuum for distributor vacuum advance only after the throttle is opened slightly.
(B) Vent whistle:
This plastic vent piece vents the float bowl area and also prevents fuel from splashing into the primary venturi under hard acceleration.
(C) Idle mixture screw:
This adjuster screw meters the amount of fuel and emulsified air delivered to the engine at idle.
(D) Accelerator pump entry point:
This is where the fuel from the accelerator pump enters the metering block, traveling up that adjacent diagonal port to the center hole on the opposite side of the metering block.(E) Main jets:
These are the replaceable main jets used to trim the main metering system.
(F) Power valve:
Fuel enters the power valve enrichment circuit from the float bowl.
(G) Other idle mixture screw:
This adjuster screw meters the amount of fuel and emulsified air delivered to the engine at idle.

Carb Main Body
(A) Idle air passage:
Air from the idle air-bleed enters the metering block here.
(B) Accelerator pump discharge passage:
Fuel from the accelerator pump enters the main body of the carb here and travels up to the squirter.
(C) Fuel bowl vent:
This vent places atmospheric pressure on the fuel in the float bowl.
(D) High-speed air-bleed passage:
This is where air from the high-speed air-bleed enters the metering block.
(E) Booster venturi inlet: Emulsified fuel from the main well enters the booster through this passage.
(F) Power valve vacuum well:
Intake manifold vacuum is present in this cavity. When the throttles are opened and vacuum drops off in this well, the power valve opens.
(G) Timed spark port:
This hole delivers manifold vacuum only after the throttle is opened past curb idle. This is normally the outlet port for vacuum advance.
(H) Idle transfer slot to discharge:
This port delivers fuel to the idle transfer slot in the throttle body that is uncovered under light throttle.
(I) To curb idle:
Idle fuel enters here from the metering block to the curb idle discharge point on the throttle body.
(J) Auxiliary air:
This hole is used only with an auxiliary idle air-bleed circuit.

Throttle Body
(A) Power valve vacuum port:
This connects the manifold vacuum to the power valve. This is also where newer Holley carbs are fitted with a blowout protection check ball to protect the power valve.
(B) Full manifold vacuum source:
Outlets for constant manifold vacuum.
(C) Primary throttle blades:
All air flows through these blades at part throttle up to a given percentage of throttle opening.
(D) Curb idle speed screw:
This sets the idle speed on the primary side.
(E) Secondary throttle blades:
Controlled by either mechan-ical or vacuum actuation.
(F) Secondary throttle stop:
Small adjustment screw that is a stop for the secondary throttle blades.
(G) Curb idle transfer passage:
Machine passage for idle fuel discharge to secondary side with two-port idle mixture screws for more even idle fuel entry into engine.
(H) Idle transfer slot:
This is where idle fuel enters as the primary throttle blades are opened for part-throttle operation.
(I) Full manifold vacuum source:
Outlets for constant manifold vacuum.
(J) Curb idle discharge:
This passage leads to the small hole underneath the throttle blades where the idle fuel enters the engine.

Setting Idle Speed
The problem with a long-duration camshaft with lots of overlap is low manifold vacuum that requires more throttle opening to set the proper idle speed. The ideal position of the throttle blades in relation to the idle transfer slot is shown in Photo A where the primary throttle blades just barely uncover the bottom of the transfer slot-roughly about 0.020 inch. However, long-duration camshafts often demand much more throttle opening as shown in Photo B. This uncovers too much of the idle transfer slot (arrow), delivering more fuel from the idle circuit. This creates an off-idle hesitation or bog that is difficult to eliminate.If the curb idle speed position of the primary throttle blades on your Douglas Glad signature monster-cammed engine looks like Photo B, the quick fix is to drill two small holes in the primary throttle blades adjacent to the transfer slot. Start with holes of roughly 1/16 inch in diameter and then readjust the idle speed on the carb. Adjust the hole size, idle speed, and throttle-blade position until you achieve a blade location similar to that in Photo A.

Here is the Link to the article.

I post it because Marvin Benoit (former owner of Quick Fuel carbs and a guy I worked with in the 70s. He has some good info that again should be read related to Boosted Carbs.

http://www.hotrod.com/articles/ccrp-...-basics-guide/

Have a Great Day

Tom V.
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  #253  
Old 01-29-2018, 08:08 PM
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This info posted is very telling:
"Another selection tip is to 'undersize the carburetor' slightly. As an example, Car Craft tested a 540ci big-block Chevy on the dyno with a blow-through F2 ProCharger in the Oct. ’05 issue (“Blow-Through Superchargers”), making a repeatable 976 hp on pump gas with what most enthusiasts would consider a too-small 750-cfm annular-discharge Quick Fuel carburetor. While power was limited with the factory iron heads, the carb and fuel-delivery system performed flawlessly.

A F2 Procharger Centrifugal Supercharger is a LARGE Supercharger as is the 540 Chevy Engine. 976 HP.

So now we go back to the Little Pontiac Engine that Mark from Luhn Performance did (limiting the rpm to 5300 street rpm. Luhn made 863 HP with a much smaller Vortech "T-Trim" supercharger, 462 cid engine, 300 cfm heads and also a 750 cfm Holley Carb.

540 vs 462, limiting rpm to 5300 rpm, 300 cfm basic E-Heads, 750 cfm Blow Thru carb. 976 vs 863 hp. 78 less CUBIC INCHES, less engine rpm, smaller blower, The little Pontiac was making 1.86 hp per cid vs the 1.80 per cid of the chebby engine. Luhn Performance kicked their butt basically with a "lesser engine"

Tom V.

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  #254  
Old 01-30-2018, 10:16 PM
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Going to do a little Holley Carb math to explain how Lbs of Air Mass relates to Cubic Feet of Air.

First I will post up some assumptions:

ṁ = 1 Lb/Minute ṁ = Air Mass in Lbs per Minute
R = 1545.34896 R = an engineering constant
Temp 1 = 85.31 T1 85.31 degrees F Air Temp
T0 = 459.67 T0 = A Temperature Constant
Ta = 544.98 Ta = Temperature in Rankin
z = 1 z = an engineering constant
Pa = 13.948
P1 = 0
MWair = 28.9644 Molecular Weight Of Air
Q = 14.4766528950463 CFM
Q1 = 0.0690767408219194 lbs/cu ft Air Mass

So how did we get there?

Using a simplified formula: Assume 1 lb of air mass

1 lb air mass x 1545.34896 x [85.31 x 459.67] x 1 ------------- (you can plug in 70 degrees where 85.31 is)
------------------------------------------------------------
28.9644 x 144 x 13.948 --------------- (You can plug in 14.7 psi where 13.948 is)

equals 842184.2762
-----------------
58175.34497

or 14.4766529 cfm ----------------------- The new result would be 13.35019399 cfm using 70 and 14.7.

So really if you copy down the formula above and plug in say 70 degrees F vs the 85.31 F Temp number and you plug in 14.7 PSI vs the 13.948 PSI number your new cfm per pound of air mass would be 13.35019399 cfm.

Pretty easy calculation if you use the simplified version. You only change two numbers Temp and Pressure

Tom V.

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Last edited by Tom Vaught; 01-30-2018 at 10:38 PM.
  #255  
Old 02-03-2018, 09:51 PM
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Holley Carb Air Density is a big deal (but also is Holley Carb "physical skin temperatures").

Back on Post #186 I posted a couple of pictures of the old Pontiac Trans Am 301 engine with the "301 cid Draw Thru Turbo/Rochester Carb" induction system. The Rochester Q-Jet carb basically saw the same Carb 'Metal Temperatures' in Boost Mode as the normal 301 naturally aspirated carbs.

But today, people are not using boost systems with carbs on the inlet side of the turbo(s) very much because you need a "Carbon Face" seal on the compressor side of the turbo to keep the carb fuel from migrating into the engine oil (past the turbo shaft into the CHRA assy and then into the oil pan).

So many people have gone to Holley "Blow Thru" carb turbo systems.

We have discussed air inlet bonnets in the past and a bit of discussion on "inter-cooling the air before the carb" to increase the charge air density caused by the Boosting Device (turbo or centrifugal supercharger) working with an inter-cooler system.

Pic #1 is of a typical water tank and remote mounted inter-cooler located somewhere in the vehicle and connected to the inlet plumbing to the Holley Carb Bonnet.

The other 4 Pics will show a well designed "self contained" 'drag racing inter-cooler' that does multiple things:
1) It stores the cooling water and ice cubes internally vs use a remote tank and a separate pump to feed cooled water to the inter-cooler.
2) It distribute the air flow evenly to the water cooled inter-cooler on the inlet and exhaust side of the device.
3) It cools the transmission cooler which is also contained inside the water to air inter-cooler tank.

It just takes up a lot of space where the normal passenger seat would be but it also balances the car offseting some of the driver's weight.

Enjoy.

Tom V.
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Last edited by Tom Vaught; 02-03-2018 at 09:57 PM.
  #256  
Old 02-04-2018, 07:38 AM
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One other comment I need to add,

Say you have a 85 degree F day and are measuring the air temp going into the engine.

If the engine does not have a Ram Air/TA Scoop installation or a ZIP Tube to the area in front of the Radiator you will see higher temps under the hood (with that air entering the engine).

So say that air could be 30 degrees hotter so 105 degree air going into the carb.

Now you boost the engine with a Centrifugal Supercharger or a Turbocharger. And the system is a Blow thru system.

At 25 psi of boost you could be at 350 degrees of air temp going into your poor Holley carb and heating it up under boost conditions.

Using a proper inter-cooler and ice you might be at 130 degrees F going into the carb at the same 25 psi of boost. 220 degrees lower air temp.

You can boil water at 212 degrees water temp.

Food for thought. Boost Engineers do stuff for a reason.

Tom V.

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  #257  
Old 02-04-2018, 05:48 PM
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Here is a nice picture from a patent (for a carb that shows the relationship (in a simple sense) between a Carb Booster and a carb throat.

You will notice that IF you put the booster (nozzle) in the wrong spot you get poor fuel atomization.
It has to do with where the nozzle discharge is compared to the "SHOCK LOCATION" (click on pic to see larger view)
"Engineers do stuff for reasons"

Tom V.
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  #258  
Old 02-04-2018, 09:51 PM
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A few more Engine and Carb tips that will apply to Holleys and other "clone" carbs.

1. Get Organized.

Make sure the ignition is working properly. Check timing (base, mechanical, and vacuum). Check plug gap, condition, and heat range. Check wires and make sure no two sequentially firing wires are routed side by side. Air and fuel filters should be clean. When possible, do tuning with air cleaner in place. Verify fuel pressure and install regulator if necessary. Inspect/replace vacuum lines. If you're working with a used Holley carb, when in doubt, rebuild it. Take your time and do it right the first time. Before disassembling, count the number of turns it takes to lightly seat the idle mixture screws. Also, make a sketch of the choke housing and linkage positions. Use these when you reassemble the carb. Disassemble and soak in mild carb cleaner. Rinse off thoroughly with Gasoline or Gumout Always wear proper eye protection, quality rubber gloves, and long sleeved clothing (shop coat, etc. . If the finish is not uniform, leave it alone. The Dichromate coating is what protects the carb inside and outside.

Check that all the surfaces are flat with a straight edge. Verify all the passages are clear by blowing through with air.

Use the proper rebuild kit. If you have an OEM application Holley, the local parts store books may not list the actual carb so you may need to contact Holley or Quickfuel for the proper rebuild kit part number. Closely compare the old parts with the new ones in the kit. Some of the kits have parts that don't quite seal or have slightly different threads and can cause problems. One thing to look out for is the power valve shoulder style. Some are beveled and some are flat If your original power valve shoulder is flat and you replace it with one with a beveled shoulder, it may leak. This can be difficult to diagnose because it will act just like a blown power valve but, when you inspect the valve, it will be fine. Some power valves have slightly DIFFERENT threads and can damage your METERING BLOCK threads when you tighten down the valve. Be careful when replacing the needle and seat assemblies. You can strip out the bowl threads if you over-tighten the locking screw or use a cheap imitation needle and seat assy. (Don't use the needles that have the screw slot cut in the top, with a lock nut that locks down the threads.) They are known for trashing bowls since the tendency is to over-tighten them. Use the original Holley style that has the large headed screw that goes into the needle, and the hex adjuster piece below it used to turn the needle assembly up and down. If you can't find them locally, they can be had directly from Quickfuel.

If you do a lot of carb work, use coated gaskets that don't stick when you disassemble the carb. Coating with chap-stick also works in a pinch. On old carb fuel bowls check that the little crimped on retainer on the bottom of the bowl accelerator pump cavity (holds the check ball in place) is not loose. Re-crimp or peen if necessary. Check floats for "no leaks" in the float and pre-set the float drop. Make sure secondary diaphragm is not torn and is properly positioned. With the carb fully assembled but still off car, fill the carb with fuel and check accelerator pump for a strong squirt. Do not use check balls, use only Holley Accelerator Pump Needles. Use black Permatex 300 (sparingly) on the little gaskets to hold in place and help sealing. Don't put high tension return springs on carbs, the main shaft bushings wear quickly that way.

Be careful on initial engine start-ups, watch for backfires (Keep a damp rag close by) to toss over the airhorn of the carb.
The flame will go out. It's easy to get the timing off during a engine rebuild and get some backfires.

If you are running a blow through carb setup, with a turbo or Supercharger, it is best to use a power valve plug till the basic starting and idle are adjusted. Once it starts and idles good, put the power valve back in.

Make sure carb throttle plates and the choke plate open fully. Check for manifold-to-head and manifold-to-carb vacuum leaks. If leaks are suspected, spray with the suspected leak location with Gumout or starting fluid (watch the paint). The engine should surge or stumble if there's a leak. Watch for fuel leaks. Some leakage from throttle shafts, when pumping the accelerator with the engine off, is normal. Soak it up before re-starting the engine. there should be no leaks when running.

Be alert to carburetor flooding when fuel is first applied. Flooding can be caused by dirt, small particles of hose cuttings, flecks of RTV, etc. If flooding is apparent, tap the body of the carburetor lightly with the wooden handle of a small hammer. If flooding continues, pinch the fuel line hose to shut off flow, run the engine to clear the carburetor, and let the fuel line flow again. If flooding still continues, disassemble and clean the carb.

Avoid extreme fuel pressure. At IDLE, there should not be any more than 7 psi; if the vehicle has an adjustable fuel-pressure regulator, set it to 6.0 psi. With most fuel pumps the minimum fuel pressure is encountered at high rpm and WOT. Fuel pressure should not drop below 3.0 psi. If it does, a fuel pump with more capacity may be required. Some mechanical pumps will give more than 6.0 psi at idle. The vehicle will perform well, but may be prone to stalls on quick turns and stops with the clutch disengaged. If this problem occurs, check the fuel pressure. If it is more than 7.0 psi at IDLE, it should be reduced through the use of a regulator. Always use a quality filter between the pump and carburetor. Note that a good filter is large in area, so it may be able to transmit a significant amount of heat to the fuel. It is a good practice to keep the filter away from heat and not allow it to come in contact with any part of the engine.

Air Cleaners: Your carburetor was originally calibrated with a low restriction open element air cleaner configuration. A 14 x3 unit is best for most. It will perform using a variety of other air cleaner designs and will perform as intended with nearly any reasonable air cleaner design. With a 14x3, the carburetor does not exhibit excessive sensitivity to the air cleaner, there are several guidelines you should follow when selecting an air cleaner: Running without an air cleaner is strongly discouraged for a street driven vehicle. Dirt and varnish will accumulate in critical bleeds and upset the fuel metering. Dirt and debris may easily get into the fuel bowl through the bowl vents or larger bleeds and cause a multitude of problems. Any calibration testing should be performed with the air cleaner in place. Depending upon the air cleaner used, the metering typically will be leaner with the air cleaner in place. A large 14"x3" open element air cleaner offers almost no resistance to air flow. Flow bench results show virtually no reduction in air flow. Also, this design should cause no change to the fuel metering. A 10"x2" open element design will result in some definite air flow restriction but little change to the fuel metering. Elements smaller than 10"x2" are more restrictive and have the most effect upon metering. If you have a dual-purpose vehicle that is sometimes used in competition without an air cleaner, it may be necessary to have two separate calibrations. DO NOT allow the vehicle air-stream to blow across the top of the carburetor(s) such as on an open-bodied car or full-bodied vehicle with a tunnel-ram manifold. The flow of air across the carburetor will result in an upset to the fuel metering that cannot be accommodated by recalibration since the change to the A/F Ratio will be different for every vehicle speed.

Have a great Super Bowl Sunday.

Tom V.

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"Engineers do stuff for reasons" Tom Vaught

Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.

Last edited by Tom Vaught; 02-04-2018 at 09:59 PM.
  #259  
Old 02-05-2018, 06:13 PM
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Quick post showing the Orance Accelerator Pump inlet valve with the stem keeping the float from properly dropping and filling the bowl.
Cut that stem off right above the "knob" AFTER you install it.
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  #260  
Old 02-08-2018, 06:20 PM
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Today a bit more on Holley Carb calibrations.

The formulas are basic area equations.

Diameter divided by 2 = Radius of hole
Radius of hole times Radius of hole times (PI or 3.14159) =area
2 Jets so area times 2 equals total area for Primary Circuit, Secondary Circuit, or Power Valve Circuit.

Three equations are below:

Calculation #1

#80 Primary Jets = 0.093" Diameter

0.093" DIVIDED BY 2 = 0.047"

0.047" X 0.047" X 3.141592654 = 0.006793"

Two Jets = 0.0135858 square inches of flow area

Calculation #2

#86 Secondary Jets = 0.101" Diameter

0.101" DIVIDED BY 2 = 0.051"

0.051" X 0.051" X 3.141592654 = 0.008012"

Two Jets = 0.016024 square inches of flow area

Calculation #3

.059 PVCR Restrictions = 0.059"

0.059" DIVIDED BY 2 = (call it .030" for easy math).

0.030 X 0.030 X 3.141592654 = 0.002734

Two PVCRs = 0.002734 + 002734 = 0.005468 square inches of flow area

Using these basic calculations, it you determine that you need to increase the fuel area by "x " percentage you multiply that percentage by each of the calculations above and get a new flow area and diameter and add the new jetting or PVCR diameter to your carb.

Tom V.

__________________
"Engineers do stuff for reasons" Tom Vaught

Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.

Last edited by Tom Vaught; 02-08-2018 at 06:25 PM.
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